For example, in a conventional electric power steering apparatus, a steering torque detected by a torque sensor as a physical quantity detecting unit is supplied to a control device as a control unit, and a current flowing in an electric motor configured to transmit a steering assist force to a steering apparatus is controlled on the basis of the steering torque by the control device.
In such an electric power steering apparatus, abnormality of the torque sensor is detected since the current to be supplied to the electric motor is controlled on the basis of the steering torque detected by the torque sensor.
In order to detect abnormality of such a torque sensor, a magnetostrictive torque sensor including failure detecting means for detecting a failure on the basis of detection results of torque detecting means and an electric power steering apparatus including the magnetostrictive torque sensor have been proposed (for example, see PTL 1).
There has been proposed a torque detecting device including a torque sensor disposed in a rotating shaft and outputting a predetermined electrical signal corresponding to a torque applied to the rotating shaft, a sensor circuit outputting the predetermined electrical signal outputted from the torque sensor as a sensor circuit signal, and an output signal processing circuit processing the output of the sensor circuit and outputting the processed signal as a torque detection signal, wherein the signal processing circuit is provided in parallel with an abnormality state monitoring circuit that operates in response to the sensor circuit signal and that monitors occurrence of an abnormal operation in the signal output from the sensor circuit such that the abnormality state monitoring circuit outputs an abnormality occurrence signal of a high level or a low level to a power steering controller when the abnormality state monitoring circuit determines that a signal involved in the sensor circuit signal is in an oscillating state (for example, see PTL 2).